Snowball put out a petrol fire (11)
I believe the answer is:
proliferate
'snowball' is the definition.
(I've seen this before)
'out a petrol fire' is the wordplay.
'out' indicates anagramming the letters.
'a'+'petrol'+'fire'='apetrolfire'
'apetrolfire' anagrammed gives 'PROLIFERATE'.
'put' is the link.
(Other definitions for proliferate that I've seen before include "Increase rapidly in number" , "Mushroom" , "Grow rapidly in number" , "spread" , "snowball" .)